This invention relates to electronic postage meters, wherein the meter includes a printing mechanism and at least one electronic register for registering a value corresponding to the setting of printing wheels of the printing mechanism. The invention is particularly concerned with this type of a postage meter, wherein the drive for the meter is obtained from the mechanical drive energy of a postal meter base, from which the postal meter itself may be removed by the operator.
In postage meter systems of one type, a postage meter is provided that is separable from a "drive base". In this type of system, as exemplified in known equipment by the Model 5300 postage meter manufactured by Pitney Bowes, Inc. of Stamford, Connecticut, and meter base Models 5460 and 5600 also manufactured by Pitney Bowes, Inc. of Stamford, Conn., the base incorporates means for driving the mechanical printing mechanism of the postage meter. A base for use in such a system is also disclosed in U.S. Pat. No. 2,934,009, Bach, et al.
In known equipment of the above type operating with primarily mechanical means, the postage meter is provided with a printing drum which may incorporate either fixed or settable postage type. The drum is driven internally of the postage meter by a drive gear, the drive gear being adapted to be coupled to a driving gear in the base when the two units are intercoupled. The postage meter further incorporates a shutter bar adapted to be mechanically intercoupled to a shutter lever on the base when two units are connected together. The shutter bar, or mechanical means coupled thereto, engage and prevent rotation of the drive gear, so that the printing of postage cannot be effective when the shutter is in its closed position. A shutter lever is provided on the driving base, for engaging the shutter bar or mechanical elements coupled thereto, to effect the movement of the shutter bar to its open position upon the initiation of a print cycle by suitable tripping means in the base. If the shutter bar of the postage meter is free to move, the shutter lever may thereby move the shutter bar out of locking engagement with the drive gear. The drive base further incorporates a clutch operative by the shutter lever so that the driving gear in the base may be driven, to in turn drive the drive gear in the postage meter, only if the shutter bar is capable of being moved to its open position. The postage meter further incorporates various blocking, or interposing means, which prevent the opening of the shutter bar in the event of certain conditions, for example, the absence of adequate postage available as stored in a mechanical register in the postage meter itself, or the mounting of the meter on an improper base.
In systems of this type, the base need not be secure, and may be a device sold as a retail item. The postage meter itself, however, is mechanically secure, i.e., it is enclosed in a secure housing so that the critical accounting and printing equipment cannot be tampered with, without rendering such tampering obvious to postal authorities.
In a primary mechanical system of the above type, postage accounting registers in the postage meter are generally of a mechanical nature, so that conditions cannot normally occur that would prevent the registration of any printing cycle to effect the storage of data corresponding to all postage that has been printed.
With the advent of economical electronic control systems, especially microcomputer systems, it is feasible to incorporate electronic accounting devices within the postage meter. Such electronic devices provide certain advantages, such as more rapid accounting of postage, to enable the use of the postage meters in high speed equipment. The electronic devices also may be more economically produced on a mass production basis, and minimize the weight, size and cost of production of the postage meter devices. Further, the provision of electronic accounting means within the postage meter renders the meter capable of additional functions that were not readily achievable in the primarily mechanical devices.
Electronic postage meters of the above type are disclosed, for example, in U.S. Pat. Nos. 3,938,095, Check, Jr., et al and 3,978,457, Check, Jr., et al.
Certain difficulties may arise in the use of an electronically accounting postage meter in combination with a base of the above described type. Thus, a problem can arise from the fact that, if a power source to the accounting registers is accidentally or intentionally removed as soon as the printing cycle has been initiated and the shutter bar has moved to release the postage meter drive, the printing cycle may be completed, but the postage printed may not be accounted since the electronic registers are unpowered.